Effects of peroperative myocardial ischemia on early and late hemodynamic response to hypertonic sodium bicarbonate in dogs.

Because hypotension induced by the administration of hypertonic sodium bicarbonate is more severe when cardiac performance is impaired, the authors evaluated the hemodynamic consequences of peroperative myocardial ischemia upon the response of conscious dogs to an intravenous bolus of sodium bicarbonate. Twenty-two control dogs (group 1) were equipped with an electromagnetic flow probe positioned around the ascending aorta. Seventeen dogs (group 2), equipped in the same manner, were subjected to 1 hour of myocardial ischemia combined with topical cardiac hypothermia. Hemodynamic studies were performed daily for 1 month before and during the administration of sodium bicarbonate. Baseline hemodynamic values in group 1 were always within normal limits. In group 2, cardiac failure was evident in the immediate postoperative period but hemodynamic values reached normal limits 24 hours postoperatively. For both groups, the peak hypotensive response to sodium bicarbonate was combined with a substantial reduction in all hemodynamic values reflecting the left ventricular performance. However, this response is significantly (p less than 0.01) more pronounced in group 2 during the first 4 postoperative days, being maximal 3 and 24 hours after operation. Afterwards, the hemodynamic response to sodium bicarbonate was similar in both groups. These results indicated that an intravenous bolus of sodium bicarbonate decreases left ventricular performance and that this decrement is greater when cardiac performance is impaired following peroperative myocardial ischemia. Long-term hemodynamic studies show that this temporary myocardial ischemia is not deleterious to cardiovascular adaptability to hypertonic sodium bicarbonate administration.